Take him to the vet!!! In the US we are fortunate to have all kinds of exotic vets. I'm sure that you'd be able to find one to help. This is a severe life threatening injury. He can go a while without eating, but the infection could prove deadly. You'll need to have him in a quiet, dark tank with SOFT hiding places (a solo cup for example). Watch the water parameters closely, any ammonia could aggravate this even more. Honestly, a vet might recommend humane euthanasia, but I really don't know. It might heal with proper treatment. Another frog couldn't have done this. Do you keep fish or inverts in the tank?
Please keep us updated.
EDIT: Also, lower the water depth if he seems to be struggling to get to the surface for air.